DASTGAH
Dastgah in Persian language means "system", as well as "equipment". The suffix "-gah" signifies the place of doing something. For instance daneshgah (university) means the place of science (danesh). Again here dastgah is used in 2 different significations: (1) the total tunes of a certain musical system, e.g. dastgah-e Shur consists of Shur, Abuata, Bayat-e Tork, Afshari, Dashti and their related gushehs; (2) the frets of a string instrument (dast means "hand", hence dastgah denotes "the place of hand").
The Persian classical music consists of seven major systems (dastgah) and five minor ones (avaz). Thus we can say that radif is the totality made by these 7 dastgahs and 5 avazes. ...